1. Field of the Invention
This invention generally relates to an electromagnetic actuator assembly for moving an accessing transducer relative to media, such as a disk, upon which information is stored for magnetic or optical accession and more particularly to an actuator assembly for moving an accessing transducer along a straight line extending radially of the media, the assembly being hereinafter called a linear actuator.
2. Description of the Prior Art
U.S. Pat. No. 3,838,445 to Barnard discloses a linear actuator for a magnetic disk storage apparatus that utilizes a cylindrical rod to guide a carriage assembly along the desired straight line path of travel relative to a rotating magnetic disk. Assessing transducers are mounted in a cantilevered manner to the carriage assembly directly overhead the guide rod, the guide rod being mounted to a baseplate to extend radially under the rotating disk along the desired path of travel. The carriage is driven by a cylindrical voice coil motor coupled to the carriage assembly. According to this patent, the mass of the carriage is concentrated about an axis that is coincident with, or closely adjacent to, the so-called axis of frictional resistance and also the axis of drive force input, which axes are aligned with the voice coil motor. Two pairs of bearings are mounted in a balanced geometry at opposite sides of the carriage assembly to keep the carriage upright on the guide rod, and one of the bearings rides against a so-called swung way to preload or bias such bearing downwardly.
Another linear actuator for use in a magnetic disk storage apparatus is disclosed in U.S. Pat. No. 3,587,075 to Brown and MacArthur. As in the Barnard patent, the actuator includes a carriage assembly, and such assembly is guided in a precise linear path by a cylindrical guide rail. A cylindrical voice coil motor is provided for exerting a bidirectional drive force at the center of mass of the entire carriage assembly. Bearings are included in the carriage assembly to contact the guide rail at three points in the same vertical plane, and such bearings are spring-biased to keep the carriage aligned with the rail. A further pair of bearings is provided at one side of the carriage to ride along a flat support rail.